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At least 1,603 records · Page 89Linked to original sources
PubMed2001

Subgingival polishing with a teflon-coated sonic scaler insert in comparison to conventional instruments as assessed on extracted teeth (II). Subgingival roughness.

AIM: To assess the root surface roughness and topography on extracted teeth using different instruments. MATERIAL AND METHODS: In the present study, laser profilometry was used to examine the 3-D roughness values Ra and Rz and topography of root surfaces of periodontally-involved teeth instrumented in vivo with curette, conventional ultrasonic device, conventional or teflon-coated sonic scaler insert, or the Periotor instrument (12 teeth per instrument type), and compare these with uninstrumented cementum surfaces. RESULTS: The roughness values Ra and Rz of the roots treated with the different instruments showed a similar pattern: curettes and the Periotor instrument produced the smoothest surfaces (Ra about 1.5 microm, Rz 30 microm); the 4 other instruments created similar Ra values of approximately 2-3 microm and Rz roughness of about 50-70 microm, which equals the untreated root surface. For Ra, the difference between the curette or the Periotor instrument and the teflon-coated sonic insert or ultrasonic insert was significant, and for Rz, a significant difference was found between the curette or the Periotor instrument and ultrasonic insert. As opposed to surfaces debrided with the Periotor and teflon-coated sonic scaler, it appears that hand instruments markedly reconfigure surfaces. CONCLUSION: The lowest root-surface roughness values were obtained with hand instruments. The teflon tubing on the sonic scaler insert effected no change of topography or roughness as compared to uninstrumented, control surfaces. However, it must be pointed out that hard-tissue removal was not investigated.

Adolescent↗
PubMedDate not supplied

Sequence-specific insertion of the Drosophila transposable genetic element 17.6.

As in the case of retrovirus proviruses, most of the Drosophila copia-like transposable elements so far examined are bounded by 5'TG...CA3' and inserted into the chromosome without obvious site-specificity. In the other copia-like elements, 297, HMS Beagle and 17.6 (refs 5-7), terminal dinucleotides (5'TG...CA3') are completely absent and, instead, 5'(A)GT is present at least at one of the termini. One important feature of these three elements may be frequent insertion into 'TATA' boxes, since the three of four insertion sites so far examined were TATA boxes, two for H3 histone genes and one for a cuticle gene. Because of the importance of this type of insertion, we extensively analysed site-specificity using 17.6 as a model. Our results, described here, suggest that insertion of 17.6 takes place in a site-specific fashion, using a target 5'ATAT corresponding to the major portion of the consensus TATA box, TATAATAAT.

Animals↗
PubMedDate not supplied

Murine T lymphomas with retroviral inserts in the chromosomal 15 locus for plasmacytoma variant translocations.

The frequent trisomy of murine chromosome 15 in T lymphomas suggests that it bears one or more genes conducive to T-cell neoplasia. One such gene seems to be c-myc, the oncogene frequently activated in B-lymphoid tumours either by retroviral insertion, as in the avian bursal lymphomas, or by a translocation to the immunoglobulin heavy-chain locus, as in the predominant t(12; 15) of murine plasmacytomas and the analogous t(14; 8) of human Burkitt lymphomas. The c-myc gene was strongly implicated in T-cell neoplasia when 15-25% of T lymphomas arising in AKR mice, a strain prone to leukaemia, were found to have retroviral inserts near c-myc. Proviruses near c-myc were also found in several T lymphomas induced by murine leukaemia viruses (MuLV) in both mice and rats, but many of the rat thymomas bear an insert instead at one of several other common sites, at least two of which have murine homologues on chromosome 15. We show here that some murine T lymphomas contain proviral inserts in the recently identified chromosome 15 locus for plasmacytoma variant (6; 15) translocations, which we have denoted pvt-1. Although 6; 15 breakpoints map cytogenetically to the same chromosome band as c-myc, the alterations of pvt-1 in tumours occur at least 72 kilobases (kb) from the c-myc promoters. The insertions in T lymphomas suggest that an altered pvt-1 locus is conducive to neoplasia in T cells as well as B cells, possibly via long-range effects on c-myc expression.

Animals↗
PubMedDate not supplied

Post-translational insertion of a fragment of the glucose transporter into microsomes requires phosphoanhydride bond cleavage.

Most eukaryotic secretory and membrane proteins insert co-translationally into the membrane of the rough endoplasmic reticulum (RER), and are targeted there by one or more NH2-terminal or internal signal sequences. However, little is known about the actual translocation and membrane integration processes. In particular, any energy requirements for targeting and integration have remained obscure because of the inability to uncouple the processes from concomitant protein synthesis. We recently showed that the human glucose transporter (GT), an integral membrane glycoprotein, can insert post-translationally into dog pancreatic microsomes with low but demonstrable efficiency in vitro, and that a fragment corresponding to the NH2-terminal 340 amino acids and 8 of the 12 membrane-spanning alpha-helixes of GT (GT-N) can insert with significantly greater efficiency. We report here that post-translational insertion of GT-N into pancreatic microsomes requires energy in the form of a phosphodiester bond, and suggest that co-translational insertion of proteins into the RER may also require energy independent of that used for polypeptide synthesis.

Animals↗
PubMed1991

RNA editing by cytidine insertion in mitochondria of Physarum polycephalum.

A corollary of the central dogma of molecular biology is that genetic information passes from DNA to RNA by the continuous synthesis of RNA on a DNA template. The demonstration of RNA editing (the specific insertion, deletion or substitution of residues in RNA to create an RNA with a sequence different from its own template) raised the possibility that in some cases not all of the genetic information for a trait residues in the DNA template. Two different types of RNA editing have been identified in mitochondria: insertional editing represented by the extensive insertion (and occasional deletion) of uridine residues in mitochondrial RNAs of the kinetoplastid protozoa and the substitutional editing represented by the cytidine to uridine substitutions in some plant mitochondria. These editing types have not been shown to be present in the same organism and may have very different mechanisms. RNA editing of both types has been observed in nonmitochondrial systems but is not as extensive and may involve still different mechanisms. Here we report the discovery of extensive insertional RNA editing in mitochondria from an organism other than a kinetoplastid protozoan. The mitochondrial RNA apparently encoding the alpha subunit of ATP synthetase in the acellular slime mould, Physarum polycephalum, is edited at 54 sites by cytidine insertion.

Amino Acid Sequence↗
PubMed2000

YidC mediates membrane protein insertion in bacteria.

The basic machinery for the translocation of proteins into or across membranes is remarkably conserved from Escherichia coli to humans. In eukaryotes, proteins are inserted into the endoplasmic reticulum using the signal recognition particle (SRP) and the SRP receptor, as well as the integral membrane Sec61 trimeric complex (composed of alpha, beta and gamma subunits). In bacteria, most proteins are inserted by a related pathway that includes the SRP homologue Ffh, the SRP receptor FtsY, and the SecYEG trimeric complex, where Y and E are related to the Sec61 alpha and gamma subunits, respectively. Proteins in bacteria that exhibit no dependence on the Sec translocase were previously thought to insert into the membrane directly without the aid of a protein machinery. Here we show that membrane insertion of two Sec-independent proteins requires YidC. YidC is essential for E. coli viability and homologues are present in mitochondria and chloroplasts. Depletion of YidC also interferes with insertion of Sec-dependent membrane proteins, but it has only a minor effect on the export of secretory proteins. These results provide evidence for an additional component of the translocation machinery that is specialized for the integration of membrane proteins.

ATP-Binding Cassette Transporters↗
PubMed1991

A 'molten-globule' membrane-insertion intermediate of the pore-forming domain of colicin A.

The 'molten' globular conformation of a protein is compact with a native secondary structure but a poorly defined tertiary structure. Molten globular states are intermediates in protein folding and unfolding and they may be involved in the translocation or insertion of proteins into membranes. Here we investigate the membrane insertion of the pore-forming domain of colicin A, a bacteriocin that depolarizes the cytoplasmic membrane of sensitive cells. We find that this pore-forming domain, the insertion of which depends on pH, undergoes a native to molten globule transition at acidic pH. The variation of the kinetic constant of membrane insertion of the protein into negatively charged lipid vesicles as a function of the interfacial pH correlates with the appearance of the acidic molten globular state, indicating that this state could be an intermediate formed during the insertion of colicin A into membranes.

Colicins↗
PubMed2000

BID-dependent and BID-independent pathways for BAX insertion into mitochondria.

In the absence of an apoptotic signal, BAX adopts a conformation that constrains the protein from integrating into mitochondrial membranes. Here, we show that caspases, including caspase-8, can initiate BAX insertion into mitochondria in vivo and in vitro. The cleavage product of caspase-8, tBID, induced insertion of BAX into mitochondria in vivo, and reconstitution in vitro showed that tBID, either directly or indirectly, relieved inhibition of the BAX transmembrane signal-anchor by the NH2-terminal domain, resulting in integration of BAX into mitochondrial membrane. In contrast to these findings, however, Bid-null mouse embryo fibroblasts supported Bax insertion into mitochondria in response to death signaling by either TNFalpha or E1A, despite the fact that cytochrome c release from the organelle was inhibited. We conclude, therefore, that a parallel Bid-independent pathway exists in these cells for mitochondrial insertion of Bax and that, in the absence of Bid, cytochrome c release can be uncoupled from Bax membrane insertion.

Amino Acid Chloromethyl Ketones↗
PubMed2003

Directed, selective insertion of single molecules into patterned self-assembled monolayers of alkanethiols with different chain lengths.

Pd(ii) pincer adsorbate molecules (1) were inserted into self-assembled monolayers (SAMs) of alkanethiols with different chain lengths (C(8) to C(18)) on annealed gold substrates. Their presence was brought to expression by reaction of with Au nanoclusters bearing phosphine moieties (2). The surface-confined Au nanoclusters were observed only on the shorter chain SAMs (C(8)SH to C(16)SH) and not on C(18)SH SAMs. This is attributed to the longer chain length of C(18)SH preventing the insertion of pincer molecules. Microcontact printing (microCP) with C(18)SH on unannealed gold substrates and the subsequent immersion of the substrates into C(8)SH, C(10)SH, C(12)SH, or C(16)SH solutions, yielded a series of patterned SAMs that have areas of thiols of different chain lengths. Insertion of 1 followed by expression using 2, or insertion of 3 showed inserted molecules only in the shorter chain SAM areas. The absolute particle densities in the former case were higher than on the corresponding homogeneous SAMs on annealed substrates, probably due to larger numbers of defects in the SAMs on unannealed substrates.

Journal Article↗
PubMed2005

Insertion reactions of hydridonitrosyltetrakis(trimethylphosphine) tungsten(0).

[W(H)(NO)(PMe3)4] (1) was prepared by the reaction of [W(Cl)(NO)(PMe3)4] with NaBH4 in the presence of PMe3. The insertion of acetophenone, benzophenone and acetone into the W-H bond of 1 afforded the corresponding alkoxide complexes [W(NO)(PMe3)4(OCHR1R2)](R1 = R2 = Me (2); R1 = Me, R2 = Ph (3); R1 = R2 = Ph (4)), which were however thermally unstable. Insertion of CO2 into the W-H bond of yields the formato-O complex trans-W(NO)(OCHO)(PMe3)4 (5). Reaction of trans-W(NO)(H)(PMe3)4 with CO led to the formation of mer-W(CO)(NO)(H)(PMe3)3 (6) and not the formyl complex W(NO)(CHO)(PMe3)4. Insertion of Fe(CO)(5), Re2(CO)10 and Mn2(CO)10 into trans-W(NO)(H)(PMe3)4 resulted in the formation of trans-W(NO)(PMe3)4(mu-OCH)Fe(CO)4 (7), trans-W(NO)(PMe3)4(mu-OCH)Re2(CO)9 (8) and trans-W(NO)(PMe3)4(mu-OCH)Mn2(CO)9 (9). For Re2(CO)10, an equilibrium was established and the thermodynamic data of the equilibrium reaction have been determined by a variable-temperature NMR experiments (K(298K)= 104 L mol(-1), DeltaH=-37 kJ mol(-1), DeltaS =-86 J K(-1) mol(-1)). Both compounds 7 and 8 were separated in analytically pure form. Complex 9 decomposed slowly into some yet unidentified compounds at room temperature. Insertion of imines into the W-H bond of 1 was also additionally studied. For the reactions of the imines PhCH=NPh, Ph(Me)C=NPh, C6H5CH=NCH2C6H5, and (C6H5)2C=NH with only decomposition products were observed. However, the insertion of C10H7N=CHC6H5 into the W-H bond of led to loss of one PMe3 ligand and at the same time a strong agostic interaction (C17-H...W), which was followed by an oxidative addition of the C-H bond to the tungsten center giving the complex [W(NO)(H)(PMe3)3(C10H6NCH2Ph)] (10). The structures of compounds 1, 4, 7, 8 and 10 were studied by single-crystal X-ray diffraction.

Journal Article↗
PubMed2004

Insertion of the amyloid precursor protein into lipid monolayers: effects of cholesterol and apolipoprotein E.

APP (amyloid precursor protein), together with Chol (cholesterol) and ApoE (apolipoprotein E), has been linked to Alzheimer's disease. We have examined the hypothesis that interaction of APP with the lipid membranes is modulated by Chol and ApoE. Insertion of APP into lipid monolayers was first evidenced as an increase in the surface pressure. APP injected into a subphase induced a substantial increase in the surface pressure of monolayers prepared from PC (L-alpha-phosphatidylcholine), Chol, SPM (sphingomyelin) and PS (L-alpha-phosphatidylserine), the major lipids present in the plasma membranes of brain cells. At a given initial pressure, the insertion of APP into expanded monolayers is higher than that in condensed monolayers, in the order Chol>PC>SPM>PS. The membrane insertion capacity of APP was also measured from surface pressure versus area (pi-A) isotherms of APP-lipid monolayers. The increase in the mean area per molecule in protein-lipid monolayers, in the order PC>Chol>PS>SPM, provides further evidence for protein-lipid interactions. These interactions occurred at optimum salt levels and optimum pH values close to physiological conditions (150 mM NaCl and pH 7.4). In addition, ApoE4 affected the insertion of APP into lipid films. APP-ApoE complexes showed a decreased ability to penetrate lipid monolayers at a constant area. APP-ApoE complexes expanded the pi-A isotherm of a Chol monolayer to a lesser extent than APP alone. These experiments demonstrate the roles of Chol and ApoE in the modulation of membrane insertion of APP.

Amyloid beta-Protein Precursor↗
PubMed2000

The membrane insertion of trichosanthin is membrane-surface-pH dependent.

Trichosanthin (TCS) is the active component extracted from Tianhuafen, a traditional herbal medicine that has been used for abortion in China for centuries. It belongs to the type-I ribosome-inactivating protein (RIP) family and can inactivate the eukaryotic ribosome through its RNA N-glycosidase activity. Recent studies have shown TCS to be multifunctional, its pharmacological properties including immunomodulatory, anti-tumour and anti-HIV activities. The membrane-insertion property of TCS is thought to be essential for its physiological effect, for it must get across the membrane before it can enter the cytoplasm and exert its RIP function. In this paper, the membrane-insertion mechanism of TCS was studied. The monolayer experiment revealed that TCS's membrane-insertion ability was dependent on low pH. Fluorescence spectroscopy using 1-anilinonaphthalene-8-sulphonic acid as a probe showed that low pH may induce the conformational change of TCS that leads to the hydrophobic-site exposure, and the CD result showed that this conformational change did not alter its secondary structure. Such conformational change leads to an intermediate state, called the 'molten globular state' by previous investigators. The pH-dependent membrane insertion and conformational change were related by the fact that the optimal membrane-surface pH needed was the same for the two events. From these and other results, a membrane-insertion model was proposed.

Cell Membrane↗
PubMed2005

Orthodontic anchorage implants inserted in the median palatal suture and normal transverse maxillary growth in growing dogs: a biometric and radiographic study.

Small osseointegrated implants inserted in the palate provide a reliable anchorage control during orthodontic treatment. When these implants are inserted in the median palatal suture in growing individuals, the possible effects on normal transverse maxillary growth are still unknown. Therefore, the aim of this study was to evaluate the influence of orthodontic anchorage implants on transverse maxillary growth when inserted in the median palatal suture of growing dogs. Five growing dogs were used, one of them randomly selected as a control dog. The test dogs each received two implants in the median palatal suture. Impressions and occlusal radiographs of the upper jaws were taken at baseline (TO), after 84 days (T1), and at the end of the study after 168 days (T2). Measurements to compare increases in maxillary width between test dogs and control dog were performed on study casts and occlusal radiographs at TO, T1, and T2. Restricted transverse growth was observed in the test dogs in the canine region. Transverse growth in the region of second and fourth premolars was similar for the test dogs and the control dog. These results may be of some clinical relevance when orthodontic anchorage implants are to be inserted in growing individuals. An alternative insertion site, for example the parasagittal region, should be considered in these cases, to avoid possible negative effects on normal transverse maxillary development.

Animals↗
PubMed1999

The use of mini-dose suxamethonium to facilitate the insertion of a laryngeal mask airway.

The use of mini-dose suxamethonium to facilitate the insertion of a laryngeal mask airway was investigated. Sixty patients were assigned randomly in a double-blind manner to receive 0.9% sodium chloride or suxamethonium 0.1 mg.kg-1 intravenously, following intravenous induction with propofol 2.5 mg.kg-1. The laryngeal mask was inserted after the first attempt in 87% of patients. Mini-dose suxamethonium improved the correct positioning of the laryngeal mask during the first attempt (93 vs. 67%, p < 0.02), decreased the incidence of swallowing (p < 0.001), gagging (p < 0.001) and head or limb movement (p < 0.05). Laryngeal mask insertion was graded as easy in 93% of patients who had mini-dose suxamethonium, compared with 60% in the placebo group (p < 0.01). The duration of apnoea between the two groups was not significantly different (0.54 vs. 0.61 min, p = 0. 46). The total dose of propofol needed to insert the laryngeal mask was lower in the suxamethonium group (2.57 vs. 3.25 mg.kg-1, p < 0. 01) and was associated with less hypotension (p < 0.05). Fasciculation (17%) and mild myalgia (23%) were common despite the small dose of suxamethonium used. In conclusion, mini-dose suxamethonium facilitates laryngeal mask insertion. Myalgia is common and the technique is not recommended for patients who are prone to suxamethonium myalgia.

Adolescent↗
PubMed1999

Laryngeal mask airway insertion using propofol without muscle relaxants: a comparative study of pretreatment with midazolam or fentanyl.

We determined the effects of pretreatment with midazolam or fentanyl on the ease of laryngeal mask airway insertion using propofol without a muscle relaxant. One hundred and eighty ASA class I or II patients were randomly allocated to one of three groups, 60 patients per group, to receive either placebo (Group C), midazolam 0.05 mg kg-1 (Group M) or fentanyl 2 micrograms kg-1 (Group F), respectively. Following intravenous administration of these drugs, Group C received propofol 2.5 (Group C-2.5) or 3.0 mg kg-1 (Group C-3.0). Group M and Group F received propofol 2.0 or 2.5 mg kg-1 (Group M-2.0, M-2.5, F-2.0 and F-2.5, respectively). There was a smaller incidence of severe head and limb movements on LMA insertion in Group M-2.5, Group F-2.0 and Group F-2.5 than in Group C-2.5. Airway obstruction and inadequate jaw relaxation, which were occasionally recognized in Group C and Group F patients, were not observed in Group M-2.5. Overall the ease of LMA insertion was significantly better in Group M-2.0, Group M-2.5 and Group F-2.5 than in Group C-2.5, however, the blood pressure in Group F after LMA insertion was significantly lower than in Group M. We conclude that pretreatment with midazolam 0.05 mg combined with propofol 2.5 mg kg-1 provides safe and satisfactory conditions for LMA insertion.

Adult↗
PubMed2002

Insertion polymorphism of retrotransposable elements in populations of the insular, endemic species Drosophila madeirensis.

The insertion site numbers of the retrotransposable elements (TE) 412, gypsy and bilbo were determined in individuals of five distinct natural populations of the endemic species Drosophila madeirensis from the island of Madeira. The TE distributions were compared to those of the paleartic, widespread and phylogenetically closely related species, D. subobscura. In situ hybridization and Southern blots showed that in D. madeirensis the number of insertion sites ranged between 10 and 15, three and six, and 35 and 42 for elements 412, gypsy and bilbo, respectively. The corresponding values for D. subobscura were similar. Two of these elements, 412 and gypsy, had very few insertions in the heterochromatin, unlike bilbo, which displayed a high heterochromatic insertion number. The Southern band polymorphism was very high, leading to within-population variation of 97.2%, whatever the population and the TE concerned. Using the polymorphic TE insertion sites as markers to analyse population structure by AMOVA, adapted for RAPD (Randomly Amplified Polymorphic DNA) data, we found small but significant genetic differences between the populations on Madeira. This slight differentiation, coupled with similar copy numbers for each TE between populations, suggests that the D. madeirensis species consists of a single, only slightly subdivided population. These data also show that insular populations and endemic species of Drosophila can have as many copies of TEs as more widespread species.

Animals↗
PubMed1998

Characterization and splicing in vivo of a Sinorhizobium meliloti group II intron associated with particular insertion sequences of the IS630-Tc1/IS3 retroposon superfamily.

By sequence analysis of Sinorhizobium meliloti strain GR4 plasmid pRmeGR4b, we have identified a group II intron named RmInt1 inserted within the insertion sequence ISRm2011-2 of the IS630-Tc1/IS3 retroposon superfamily. Like some other group II introns, RmInt1 possesses, in addition to the structurally conserved ribozyme core, an open reading frame (ORF) with homology to reverse transcriptases. Using a T7 expression system in Escherichia coli, we show that the intron is active in splicing in vivo and that splicing efficiency requires the intron-encoded ORF, which suggests that the putative intron encoded protein has a maturase function. DNA hybridization studies indicate that intron RmInt1 is widespread within S. meliloti native populations and appears to be mostly located within this IS element. Nevertheless, some S. meliloti strains harbour one copy of RmInt1 at a different location. DNA sequence analysis of the 5' exon of one of these heterologous intron insertion sites revealed the presence of a putative IS element closely related to insertion sequence ISRm2011-2. The intron-binding sites (IBS1 and IBS2 motifs) are conserved, although a transition of a G-->A in the IBS1 has occurred. Our results demonstrate an association of intron RmInt1 with particular insertion sequences of the IS630-Tc1/IS3 retroposon superfamily that may have ensured the spread and maintenance of this group II intron in S. meliloti.

Amino Acid Sequence↗
PubMed1999

Multiple insertions of fimbrial operons correlate with the evolution of Salmonella serovars responsible for human disease.

On centisome 7, Salmonella spp. contain a large region not present in the corresponding region of Escherichia coli. This region is flanked by sequences with significant homology to the E. coli tRNA gene aspV and the hypothetical E. coli open reading frame yafV. The locus consists of a mosaic of differentially acquired inserts forming a dynamic cs7 region of horizontally transferred inserts. Salmonella enterica subspecies I, responsible for most Salmonella infections in warm-blooded animals, carries a fimbrial gene cluster (saf) in this region as well as a regulatory gene (sinR). These genes are flanked by inverted repeats and are inserted in another laterally transferred region present in most members of Salmonella spp. encoding a putative invasin (pagN ). S. enterica subspecies I serovar Typhi, the Salmonella serovar that causes the most severe form of human salmonellosis, contains an additional insert of at least 8 kb in the sinR-pagN intergenic region harbouring a novel fimbrial operon (tcf ) similar to the coo operon encoding the CS1 fimbrial adhesin expressed by human-specific enterotoxigenic E. coli. It is suggested that the multiple insertions of fimbrial genes that have occurred in the cs7 region have contributed to phylogenetic diversity and host adaptation of Salmonella spp.

Chromosome Mapping↗